Initial structuring for URIToUID API

src/github.com/matrix-org/dendrite/appservice/routing/routing.go

@@ -51,11 +51,7 @@ func Setup(
 	).Methods(http.MethodGet, http.MethodOptions)
 	appMux.Handle("/user",
 		common.MakeExternalAPI("user", func(req *http.Request) util.JSONResponse {
-			// TODO: Implement
-			return util.JSONResponse{
-				Code: http.StatusOK,
-				JSON: nil,
-			}
+			return URIToUID(req)
 		}),
 	).Methods(http.MethodGet, http.MethodOptions)
 }

src/github.com/matrix-org/dendrite/appservice/routing/user.go

@@ -0,0 +1,25 @@
+package routing
+
+import (
+	"github.com/matrix-org/util"
+	"net/http"
+)
+
+// represents response to an AppService URI to User Id
+// (/_matrix/app/r0/user?uri={url_encoded_uri}) request
+type URIToUIDResponse struct {
+	UserID string `json:"user_id"`
+}
+
+// URIToUID implements `/_matrix/app/r0/user?uri={url_encoded_uri}`, which
+// enables users to contact appservice users directly by taking an encoded
+// URI and turning it into a Matrix ID on the homeserver.
+// https://matrix.org/docs/spec/application_service/unstable.html#user-ids
+
+func URIToUID(req *http.Request) util.JSONResponse {
+	// TODO: Implement
+	return util.JSONResponse{
+		Code: http.StatusOK,
+		JSON: nil,
+	}
+}